The S-100 Bus - John Dunn, Consultant, Ambertec, P.E., P.C.

The venerable TRS-80, the first one, had a digital interface which was nice and simple and which could be accessed pretty easily. As the model was at the time being phased out by Radio Shack, we decided to buy several of them at really low cost and to convert them into some automatic test equipment for a line of digitally controlled high voltage power supplies.

There was one Radio Shack store nearby which we heard through the grapevine had a stock of those little computers which they wanted to unload so I went over there to select however many good ones I could find. I found three.

I finished finding them just in time too because the store was about to be commandeered by a local computer club whose meetings were regularly held at five PM each Wednesday. I saw the members starting to arrive. The artist Al Hirschfeld would have had a field day with this bunch.

There were two who particularly caught my eye. One was an older man, maybe fiftyish, somewhat overweight, with longish, graying hair and a Gabby Hayes (Go ahead, look him up.) type beard and the other was a really tall, very skinny teenager with longish straight blond hair that kept wanting to fall in front of his eyes and who had this perpetually angry stare.

The two of them were engaged in a highly animated discussion / argument about something, exactly what I wasn't sure. At one point, the older man said: "You know, the S-100 bus can't support that." to which the younger one replied, stiff backed: "I know everything about the S-100 bus!"

I could barely contain myself. I wanted to go over and say "Hello! What an honor. I've never met anyone who knew everything about any particular topic.", but I let my better judgment prevail and didn't say it.

Comments

[Chuck Blevins]

Wow, there is a blast from the past. I designed an S-100 disk emulator with 256KB of DRAM in the early 80's. It certainly sped up compilation compared to an 8 inch floppy disk. I don't remember the TRS-80 having an S-100 bus. I developed my product on an Altair S-100 computer. I still have that machine in my man cave. I always thought that the onboard 5V regulator for each board was ahead of its time (Point of load) The TRS-80 did one important thing. It brought the computer to the masses.

[John Dunn]

Hi, Chuck.

You are right. The TRS-80 did not use the S-100 bus. That came from Altair.

It's just that I was looking for used TRS-80s when I overheard that memorable discussion.

All the best!

John

[Rudy Schneider]

I agree with Chuck --- that was definitely a blast from the past! My first computer was an S-100-based, linear power-supplied behemoth. Somehow, I managed to NOT break my back hefting it into and out of the trunk of my car to-and-from work each day (even I can't remember why!). I used it for some word processing and wrote an assembler to support some of of my early 8085 developments. Ahhhh, memories...